The primary structural component of a bicycle is the bicycle frame. Typically, the bicycle frame comprises an elongate cross bar which is rigidly secured to and extends between a head tube of the bicycle and a seat tube of the bicycle. The heat tube typically provides a structural base for the stem of the bicycle to which the handlebars are attached. The seat tube provides a base for a seat post which is generally telescopically received therewithin and to which is secured the saddle or seat of the bicycle. In typical bicycle frame construction, the seat tube includes a generally cylindrically axle-receiving bracket attached to the lower end thereof which is adapted to receive the bottom bracket axle. The bottom bracket axle typically extends between and interconnects the cranks to which are attached the pedals. Rigidly secured to and extending between the head tube and the cylindrical axle-receiving bracket is an elongate down tube.
In addition to the aforementioned structural components, rigidly secured to and extending rearwardly from the axle-receiving bracket are first and second chain stay members. Additionally, rigidly secured to and extending downwardly from the upper end of the seat tube are first and second seat stay members having distal ends which are rigidly secured to the back ends of the first and second chain stay members. Typically, the distal ends of the seat stay members and back ends of the chain stay members are interconnected in a manner adapted to receive the rear tire axle of the bicycle.
The foregoing description generally represents the construction of conventional prior art bicycle frames. Typically, once such prior art frames are constructed, the aforementioned structural components are rigidly secured to one another through the use of welding or brazing techniques. Though this method of constructing the bicycle frame provides the resulting frame with structural integrity, the bicycle frame does not possess a suspension having shock absorbing characteristics. As will be recognized, the ride, comfort and performance of the bicycle would be greatly enhanced if the bicycle frame were adapted to at least partially accommodate the shocks routinely encountered while riding the bicycle.
Though recent prior art bicycle frames include front and/or rear shock absorbing assemblies, such bicycle frames possess certain deficiencies which detract from their overall utility. In this respect, the manner in which the rear shock absorbing assemblies are typically interfaced to the seat stay members of the frame creates a significant amount of lateral instability for the rear wheel of the bicycle. As will be recognized, such instability severely diminishes the performance and handling characteristics of the bicycle. Additionally, many currently known rear shock absorbing assemblies create slop within the chain during normal and vigorous pedaling, thus adversely affecting the performance of and speed obtainable with the bicycle. Further, in most prior art rear shock absorbing assemblies, the rear axle pivots about a single point when subjected to a shock force which results in the pedaling forces either compressing or extending the shock absorber of the rear suspension, and/or the rear tire axle moving in a direction other than parallel to the direction of the shock force applied to the rear wheel. In this respect, when the shock absorber of the rear suspension is affected by the pedal force, some of the riders' energy is needlessly wasted to activate the shock absorber. Additionally, when the rear tire axle moves in an arc that is not tangent to the direction of the shock force applied to the rear wheel, riding efficiency is lost.
As previously specified, the rear suspension is often affected by the pedal force, thus causing some of the rider's energy to be needlessly wasted. In this respect, a problem common to most prior art rear suspension systems is the tendency of the rear suspension system to either lock-up or "squat" when the rider pedals aggressively. Since these prior art rear suspension systems are generally designed having a single lever arm which pivots about a single point, the lock-up or squat generally occurs as a result of chain tension acting on the single lever arm. If the single pivot point of the rear suspension system is above the chain line, the system will typically lock-up, thereby providing suspension only when the shock or bump force exceeds the chain tension. Conversely, if the single pivot point of the rear suspension system is below the chain line, the system will typically squat since the chain tension is acting to compress the shock absorber of the rear suspension system in the same manner as does the shock or bump force. The present invention specifically overcomes these and other deficiencies associated with prior art bicycle frames.